1. Field of the Invention
The present invention relates to the electromagnetic release field, more particularly, relates to an adjustable electromagnetic release for large capacity circuit breakers.
2. The Related Art
Circuit breakers are electrical apparatuses for cutting off fault current such as overload current or short circuit current in circuits so as to protect circuit loads. The circuit breakers cut off the short circuit current via releases. The releases for cutting off short circuit current mainly include electromagnetic releases and electronic releases.
Usually, the releases are required to have different protection scopes in different working environments. Such requirements mean that the releases shall have adjustment abilities so as to satisfy different scales of short circuit current. FIG. 1 illustrates the structure of an electromagnetic release in the prior art. As shown in FIG. 1, according to the existing electromagnetic release, an air gap of an electromagnet is reduced via adjustment of an armature. When adjusting the air gap, a reaction spring is stretched and a resistant force of the spring is enlarged meanwhile. Therefore, there are two variables existed in the adjustment, when the initial attraction force enlarges, the initial reaction force enlarges as well. Such an adjustment mode is detrimental to the release rate adjustment of the release. This adjustment mode has low accuracy, sometimes it is not able to obtain the required release rate. Further, when adjusting the air gap, the required adjusting force may be very large due to the function of the reaction spring force, which may cause the adjustment be very difficult. If the material is not strong enough, the adjusting components may be damaged and will cause the circuit breaker be not adjustable.